Friction is the resistance of one solid sliding over another solid; often the higher the friction the greater the wear of materials. The best way to reduce friction and wear is by separating the surfaces; this can be accomplished by the use of a liquid lubricant such as oil. The ideal condition is known as hydrodynamic lubrication and can eliminate wear by fully separating materials by a fluid film. Ideal conditions of hydrodynamic lubrication are rarely maintained in practice. Starting, stopping, misalignment, heavy loads and other conditions can cause the fluid film to be squeezed out, or allow surface asperities to break through the lubricant film, so that the two solids are pressed into contact with one another. Ideal hydrodynamic lubrication ends, and elastohydrodynamic or boundary lubrication begins. If no liquid is present the surface is either self lubricated (no lubrication) or a solid lubricant can be used. Solid film lubrication is a critical enabling technology employed in the absence of liquid lubricants. The choice to forgo a liquid lubricant or grease can be either by design constraints or by operating conditions being too severe for liquid and grease survival. Extreme operating conditions are typically defined by severe environments (e.g., water, chemicals), temperatures, and pressures. Extreme operating conditions require a distinct and separate class of lubricants. The harsh environment of outer space or internal combustion engines is marked by such extreme conditions and has spurred the development of a special class of lubricants which are not organic based. The extreme operating conditions found in space sometimes preclude the use of conventional liquids and greases. Solid film lubricants have been very successful in fulfilling the role of providing wear protection in such conditions. Relative to liquid lubricants, solid lubricants generally have lower vapor pressures, better boundary lubrication properties and relative insensitivity to radiation effects, and operate in wider temperature ranges.
Successful solid film lubricants are characterized by the following properties:                low shear strength        high adhesion        low abrasivity        thermo-dynamic stability.        
For moving mechanical components these properties are essential to reduce metal on metal contact and thereby reduce friction, heat, and wear. Much work has been done in identifying materials which have the above properties. Generally, but not exclusively, there are 3 distinct classes of soft solid film lubes meeting these criteria:                Graphite (DLC, although carbon based, is not a soft solid film)        Dichalcogenides of molybdenum and tungsten        Soft MetalsGraphite        
Graphite is the stable form of carbon. The bulk lubricating properties of graphite have been known as early as 1906 and the dichalcogenides as early as 1939. [3] Graphite is used extensively in the electrical industry for its good lubrication properties as well as its good electrical conductivity. Graphite is a durable, heavy-duty lubricant that can endure extreme temperature fluctuations ranging from −100 C to 350 C. Graphite has a sheet like structure where the atoms all lie in a plane and are only weakly bonded to the graphite sheets above and below. The C—C bond is strong in 2 dimensions but weak in the third with a hexagonal crystal orientation. Much like a deck of playing cards, the sheets slide easily. Graphite provides the best wear protection in the presence of moisture.
Dichalcogenides of Molybdenum and Tungsten
The dichalcogenides of molybdenum and tungsten meet the successful solid film lubricant criteria very well and have been used extensively and successfully on most space missions (vacuum & temperature extremes) since the late 60's. MoS2 is a naturally occurring mineral, formed and mined with other ores in various parts of the world. It is highly refined and processed into 0.5-micron average particle size at which time it can be used as a solid lubricant. It possesses the properties of being able to withstand extremely high load capacities up to 600 ksi. It is chemically stable, has a very low coefficient of friction, 0.05 to 0.09, in powder form and has thermo-stability from cryogenic temperatures to 350 deg. C. MoS2 is an ideal solid film lubricant material for extreme environments.
On an atomic level the dichalcogenide lubricants, have a hexagonal crystal structure with strong cation bonded layers creating a basal plane sandwiched between two weekly bonded anions (Van der Waals forces). The net effect is similar to a deck of cards sliding parallel to the long axis, the sliding axis, producing very low friction between mating surfaces. As a rule of thumb MoS2 is the preferred lubricant for vacuum/cryogenics and graphite works the best in air, graphite relying on moisture to induce the proper shear.
The first major milestones in thin solid film lubricant technology are when T. Spalvins in 1967 at NASA Lewis, first reported on the properties of sputter vacuum deposited MoS2 films and subsequently B. C. Stupp in 1968 started to commercially provide PVD deposited MoS2 coatings in Dayton, Ohio. PVD processing resulted in the highest adhesion solid film lubricant coatings.
Soft Metals
In addition to the dichalcogenide and graphite lamellar type films, soft metals such as Au, Ag, In, Cr, Pb can provide wear protection under extreme conditions and meet the requirements of successful solid film lubrication. Soft metallic lubricants have crystal structures with multiple slip planes and do not work-harden appreciably during sliding contacts. Dislocations and point defects generated during shear deformation are rapidly nullified by the frictional heat produced during sliding contact. Reported friction coefficients of soft metals range from 0.1 to 0.4, depending on the metal and test conditions. Ion-plated lead films are extensively used in Europe. In solar array drives alone, more than 2 million operational hours in orbit have been accumulated. An important property of the lead film is its high load-carrying ability. Under Hertzian contact, the as-deposited film flows plastically until a thin film (10 Nm thickness or less) remains and then elastically deforms the substrate. In this condition, the film can survive contact loads approaching the static load capacity of a rolling element bearing. Lead coatings have had good success as a solid lubricant in vacuum applications and additionally it is used extensively as a solid film lubricant for the high speed bearing in imaging X-ray tubes under vacuum. Optimum performance of lead and other metals is achieved at approximately 1 um thickness. Silver and indium have been investigated too, but actual usage in space is not reported. Solid lubricant films are used in a variety of mechanisms on various spacecraft and launch vehicles. Deposition of soft metals (Pb, Au, Ag, In) by ion plating provides excellent adhesion. These films have been particularly effective in spacecraft bearings found in solar array drive mechanisms in European satellites, on the Hubble space telescope and the BAXS gear for the International Space Station solar collector gear drive. Gold and silver are used in situations requiring electrical conductivity as well. Sputter-deposited MoS2 has a lower coefficient of friction than ion-plated Pb 0.01 versus 0.1, which means that MoS2 components should develop less torque.
There are other lubricant materials that have been reported, but they only find application in limited conditions. For example, CaF2, BaF2 and cesium oxythiomolybdates/tungstates have been used for high temperature lubrication. They become soft and their shear strength decreases as the temperature increases.
Today there are many industrialized methods of solid film lubricant deposition for extreme environments. The general categories in order of increasing cost, complexity and adhesion are as follows:                Burnished Powders        Painting with VOC and Binders        PVD Vacuum Deposited        
Burnished Powders; Solid film lubricants or other functional materials are mixed and placed on a carrier material such as a cloth, blasting media, inert media or specially designed fixtures. The parts to be coated are then brought in contact with the various media resulting in a film of the solid lubricant on the surface of the part. The lubricant material is marginally adherent to the surface of the part with a mechanical bond at best.
Painting Methods; Solid film lubricants or other functional materials are mixed with organic solvents as well as binders and parts are coated by paint spray guns, dipping or spin coating. Parts must be grit blasted prior to coating. Blasting results in surface finish degradation as well as fatigue from stress risers. Once the parts have been coated an oven bake out procedure is required to evaporate the solvents as well as cure the binders. These methods require the use of VOC's, and are not environmentally friendly. The bond between the solid film lubricant and the part to be coated is limited by the mechanism of the binder and how well it can glue the solid film lubricant to the surface; this bonding is not very strong and the resultant coating can become thick and affect part tolerances. The binders tend to introduce impurities and increase the coefficient of friction of solid film lubricants versus their pure form.
Vacuum Methods; Solid film lubricants or other functional materials are Physical Vapor Deposited (PVD) using sputter or ion plating deposition. Parts are placed in a chamber which is evacuated of atmospheric gases by pumps. The functional material cathode is bombarded by ions to dislodge the coating on an atomic scale on to the surface of the parts to be coated. This coating tends to have strong bonding to the part due to the purity of the process but requires expensive equipment and complex process control. Limitations exist on the size and shape of the parts to be coated based on the chamber size as well as ability to effectively manipulate the part for this line of sight process.
Solid film lubricants are critical for providing low friction surfaces especially in extreme environments. There exist many patents for applying solid film lubricants in special applications found across the majority of industry. Examples include automotive, internal combustion engines, aerospace, gas turbine engines, molding, glass manufacturing, welding, swaging, bearings, cabling and conveyor systems, cutting and forming tools; and many others. The primary methods of solid film lubricant deposition includes spraying, dipping, rubbing, tumbling or brushing. With these primary deposition methods the solid film lubricant must be added to another medium such as epoxy, resin or wax or grease to achieve some level of adhesion to the part being coated; additionally a post oven bake is required. The addition of such binders results in films which are thick and often brittle. An alternative method is to add solid film lubricants to metallic particles and then to use thermal spray methods to deposit low friction coatings. This method results in only a mechanical bond and often post coating grinding and or polishing is required. Some technologies apply solid film lubricants to the surface of parts by mechanical impingement using sand blasting equipment or tumbling polishing equipment however bonding is very weak and surfaces must be roughened prior to coating to create divots to hold the solid film lubricant. Methods based on PVD do achieve atomistic adhesion and a thin film structure with excellent tribological characteristics however these PVD sputtering process requires expensive vacuum equipment and sophisticated process controls. Solid film lubricants deposited by PVD have the ultimate performance capabilities as well as the smallest market share.
Thus, there is need and market for a method to durably attach a functional layer to an object having one or more surfaces or to a substrate, that overcomes the above prior art shortcomings.
There has now been discovered a method for adhering a functional layer to a substrate or 3-D article, by a convenient and low cost method along with a novel product, the laminate so formed.